How bad could the air quality in Western Washington be as the wildfires hit third?

Air quality is very bad in central Puget Sound and around Bellingham today.

Unhealthy with high concentrations of nuts can travel deep into your lungs.

Around 6 p.m., the latest purple air map shows a nasty story with the most severe air pollution shown in purple. Seattle and its eastern suburbs are in dire straits.

In fact, in Seattle, today’s air quality problems are only remedied by September 2020 conditions, as shown by this chart available on the Clean Air Authority website Puget Sound for their Duwamish observation sensor.

Compare satellite imagery today and during the 2020 event (see below). There is no contest. WAY more smoke in 2020.

The 2020 fires burned more than a million acres in the Northwest. Our fires this month are about 1/20 of that.

This was actually a very low fire year in Washington, as measured by burned area.

Smoke in Seattle is mainly coming from two fires. Loch Katrine east of Duvall (about 1600 acres) and Bolt Creek Fire (about 15,000 acres). The fire has also not grown much in the past few days.

So why is it so bad in Seattle?

There are three reasons: the proximity of the fires, their altitude, and the inversion.

Let’s start with the inverse, where the temperature increases with height.

On Monday, cool moves in at a low level with warm air above, creating an inversion. Inversions act as barriers to vertical air movement, and our inversion is about 3000-5000 ft above the surface.

As noted in my previous blog, the inversion is protective at first, preventing smoke from distant fires from reaching the surface. But inversions have a dark side to them: if the smoke is underneath, it’s difficult to mix the smoke out.

Seattle at noon today

And that’s the second difference – the location and altitude of the fire.

The Loch Katrine Fire is very, very close to the urban area and is very low-level (2500-3000 ft). So it can spew smoke BELOW inversion where it will remain in high concentration. And close means less space to diffuse horizontally.

The Bolt Flame is also at a relatively close and lower altitude.

In the past few years, we have not seen such low-altitude fires near Puget Sound.

Fortunately, relief is near at hand. Then tomorrow, inshore currents will increase and air quality will rapidly improve. Rain will really come on Friday. A welcome change.

Finally, some people and the local press consider this smoky event to be a harbinger of the future, a symptom of global warming. Good science suggests the opposite. I will discuss this in a future blog.

Question: If the Loch Katine Fire started on September 2 and was only 2 acres a week ago, why wasn’t it put out? Without this fire, the smoke in Puget Sound would be MUCH less.


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